With the photosensitivity of the amorphous silicon, input displays are provided with the embedded photo sensing elements formed thereby. Since the process of the amorphous silicon photo sensing elements and the readout circuit layout of an input display are compatible with the known process of the thin film transistor array of the active matrix liquid crystal display, the manufacturing cost of the input display with embedded amorphous silicon device as the photo sensor is more competitive than the known input display with a sensitive film attached thereon.
Furthermore, the optical transmittance of the input display with the sensitive film would be degraded by 20%; while the optical transmittance of the input display with amorphous silicon as the photo sensing elements is only dependent on the layout of the photo sensing elements and the readout line in each readout pixel. Therefore, if the photo sensing elements and circuit layout in each pixel are well designed, the aperture ratio in each pixel of the input display is rarely affected.
Please refer to FIG. 1 which schematically shows a detailed layout of a photo sensing element in a readout pixel of an input display according to the prior art. As can be seen from FIG. 1, the photo sensing element includes a photo TFT 121 as a photo sensor for generating a photo current transmitted through a switch TFT 122 and then read out through the transmission of the readout line. The drain and gate terminals D, G of the photo TFT 121 are connected to a bias voltage, and the source terminal S of the photo TFT 121 is connected to the readout line of the readout pixel through the switch TFT 122. As can be seen from FIG. 1, the drain terminal D of the switch TFT 122 is connected to the source terminal S of the photo TFT 121, and the gate and source terminals G, S of the switch TFT 122 are connected to a gate line of and the readout line of the readout pixel, respectively.
Furthermore, please refer to FIGS. 2(A) and 2(B), which shows the layout of the connecting pads, such as gate pads, data pads and readout pads on the substrate of a liquid crystal display. As can be seen from FIG. 2(A), the gate pads 55 and data pads 45 in a normal liquid crystal display are respectively arranged on two adjacent sides which are also called gate side and data side of the liquid crystal display. The gate pads 55 and data pads 45 are used for connecting each of the gate lines and data lines to the respective gate and data drivers, so that the gate signals and data signals from the respective gate and data drivers can be inputted into each gate line and data line for driving the active region of the display. However, in the input display, the readout lines are additionally provided for transmitting the photo signals generated by the photo sensing element of the input display, as can be seen from FIG. 2(B). Therefore, it is necessary to arrange an additional readout pads 35 for connecting each readout line to the readout IC(s) (not shown). If the number of readout lines are increased, it is necessary to arrange an additional margin area 33 on the substrate of the input display for disposing those readout pads 35, so that the bonding process of the readout IC can be carried out thereon. Since there will be the additional margin area 33 provided for the readout pads 35, the module process of the input display would be incompatible with the original module process of the liquid crystal display. Therefore, it is necessary to improve the layout of the readout line 31 and the readout pad 35 of the input display, so as to make the module process of the input display can be compatible with that of the original liquid crystal display.
Based on the above, it is the main aspect of the present invention to provide a novel layout design of an input display for simultaneously retaining the aperture ratio and enhancing the photosensitivity thereof.